INTRODUCTION. CXXXlll 



in any recent systematic work. Whether it ever became 

 current at all, I am not aware ; but it seems to have 

 lapsed ; and it is therefore perfectly allowable to give the 

 term another application: 



The most plausible objection to the retention of Thomp- 

 son's name is founded on his own mode of defining it. 

 He uses Polyzoa in the singular number, and describes it 

 as " a new animal discovered as an inhabitant of some zoo- 

 phytes." It is argued that he evidently employed the 

 name to denote the polypide merely, and that to make it 

 a class-designation would be to give it a totally different 

 sense from that which he intended *. This reasoning, it 

 seems to me, proceeds on a complete misapprehension of 

 his meaning. He used the term Polyzoa (in opposition to 

 Hydra) to denote a distinct type of structure, which he had 

 demonstrated, and not as the mere name of the single 

 zooid. This is evident from the following, amongst other 

 passages : — " The Polyzoa will probably be found in many 

 dissimilar genera of the zoophytes, and even mixed up with 

 Hydra in some; . . . and hence this discovery must be the 

 cause of extensive alterations and dismembermeuts in the 

 class with which they have hitherto been associated. ... I 

 shall merely indicate here in a general way the whole of 

 the Flustraceee, in many of which I have clearly ascertained 

 the animals to be Polyzoa ;" which is equivalent to saying 

 that they exhibited the new type of structure, and were 

 thus distinct from the Hydra. In a word, Polyzoa, as he 

 uses it, is essentially a class- designation, and not the name 

 of a mere structural element. 



His Polyzocs were polypes exhibiting a molluscan orga- 



* See a paper by Mr. A. W. Waters, Proc. Manchester Lit. & Phil. Soc, 

 Microscop. & Nat. Hist. Section, March 11, 1878; Ann. N. H. Jan. 1880. 



